All I have ever run is the plastic (nylon) and never had an issue. We even used it on the track and no one ever said a word. I always run it along the wiring harness and zip tie it every few inches. I keep it away from anything hot and sharp. I have however, seen copper line break and it had more than one loop in it. If you don't want the nylon line then I would go with braided.
I was going to run the nylon, but some of the previous posts have me second guessing that. Once the compression nut is lightly seated, how much additional tightening torque is required to secure it without pinching the line.....1/4-1/2 or more?